In the art of portable rotary power tools such as screw drivers and the like it is conventional practice to provide for a variety of nose portions of the tool housing which are removable from the main housing member and which are each adapted to mount a specific type of bit retaining device, namely, the conventional slip chuck for screw driver bits or wrench socket drivers, a screw finder and bit assembly, and special screw holding devices in combination with a rotary bit. Accordingly, it has heretofore been necessary to not only have available the various bit and fastener holding devices, but also special housing portions specifically adapted to mount the respective devices used with rotary screw drivers. Such arrangements are expensive and require that additional housing nose portions be used for each type of bit, bit driver, or screw holding device.